Meaningful Change | HQCA Focus

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Meaningful change

What is Statistical Process Control?

FOCUS on Healthcare uses an advanced analytical technique called statistical process control (SPC) to help you determine what variation is worth investigating so you know where to direct your quality improvement effort.

Everything we measure varies. Highlighting meaningful change through SPC helps you understand whether data is varying naturally or if a situation is experiencing unexpected progress or regression.

In an emergency department, there are expected variations from day-to-day with patient volumes and acuity. However, unusual variation might occur when there is a staffing issue or an influx of patients because another emergency department temporarily closed.

Putting pandemic years in perspective

Our SPC-powered charts were built so you can detect meaningful change amid the unique circumstances (pre-pandemic; pandemic; and post-pandemic) at emergency departments in recent years.

Pre-pandemic is the time prior to March 11, 2020 when the World Health Organization declared a global pandemic for COVID-19. The pandemic years in Alberta are generally seen as March 11, 2020 to March 1, 2022. The post-pandemic years include the shift to endemic from March 1, 2022 when the Alberta government lifted most health restrictions to now.

When using the charts…
Use your cursor to hover over specific sections of the data to see which SPC rules apply. You can also hover over the Legend for more detail on SPC rules.



Questions to reflect on

If the chart shows ONLY expected variation:

  • Is the centre reference line (the mean) result acceptable? If not, you  could consider implementing changes to move the system toward a more desirable mean result.
  • Is the range of expected variation (between upper and lower limits) acceptable? If not, you could focus on understanding why this is and then look to minimize the variation and make your system more predictable.

If the chart shows ANY unusual variation:

  • What may have caused the results for this period of time to be different than the results at other times?
  • Is there an action that could be taken to resolve or eliminate a cause of deteriorating results?
  • Is there an action that could be taken to learn from, sustain, or spread an improvement?

Rules for detecting meaningful change

Unusual variation is found by applying five rules based on probability.

Rule 1 – A sudden change has occurred: 1 point outside the control limits.

Rule 2 – A change has occurred: 2 out of 3 points are near the control limits (in the outer one-third of the chart).

Rule 3 – A shift has occurred: 8 or more points in a row above (or below) the centreline.

Rule 4 – A trend has occurred: 6 or more points in a row increasing or decreasing.

Rule 5 – Reduced variation has occurred: 15 or more points in a row close to the centreline (in the inner one-third of the chart).